wesm

I have been chasing a backfire problem with my 93 LT1 (vette) engine that I installed in a Jeep. The backfire problem was intermittent and engine would also surge without any throttle position changes and seemed to lose power just before a backfire. Let off the gas and then it would run great. Fuel pressure is correct, O2 sensors, plugs, wires, Opti and all of the sensors for that matter are all new. I should also add that the exhaust is pacesetter headers with custom 2.5" y-pipes to a 3" exhaust and 3" magnaflow muffler. I added bungs for O2s to the Y pipes just downstream of the header collectors on both sides. EGR deleted from ECM and removed from engine.

Running datamaster, I got a DTC64 (right bank lean) so I pulled the passenger side O2 sensor and replaced with a new one (it was fouled). Backfire problem continued - so I unplugged both O2 sensors and now it runs great - no surging, smooth idle, and strong acceleration. I read a post that said with speed density and no cats, you really do not need O2 sensors since ECM will use factory AFR. Should I continue to chase this problem to maximize performance or enjoy a smooth running engine without the O2s?

shbox

My guess would be your O2s are not heating up enough. Downstream from the collector may be too far, especially for a non-heated O2. Changing the placement or modifying it for heated O2s may help.